Providers - generation ?

[c***@gmail.com]

Hi all,

I apologise if my question sounds silly or badly grounded.

I am working on a project which makes intense use of Google Guice and I've
seen several places where the class I am working with uses injected
providers, such as:

class WhatEver {
@Inject
WhatEver(Provider<A> providerOfA ...) { ... }

}

I do not understand how/what implements the provider as I do not see any
class around my module explicitly implementing the interface.

Provider<A>


I am pretty sure there is not any.

How does that work ? Are providers synthesised/generated ? If yes I would
like to see where this is done - so I can have a better idea about how the
whole thing works.

Thanks in advance,
Pietro.

[Stephan Classen]

Yes, Providers are generated on the fly by guice.

https://github.com/google/guice/wiki/InjectingProviders

Post by c***@gmail.com
Hi all,
I apologise if my question sounds silly or badly grounded.
I am working on a project which makes intense use of Google Guice and
I've seen several places where the class I am working with uses
|
classWhatEver{
@Inject
WhatEver(Provider<A>providerOfA ...){...}
}
|
I do not understand how/what implements the provider as I do not see
any class around my module explicitly implementing the interface.
|
Provider<A>
|
I am pretty sure there is not any.
How does that work ? Are providers synthesised/generated ? If yes I
would like to see where this is done - so I can have a better idea
about how the whole thing works.
Thanks in advance,
Pietro.
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[c***@gmail.com]

I was reading that page but I can't find where it explicitly says they are
generated. Would you know where the code that generates them is ?

Post by Stephan Classen
Yes, Providers are generated on the fly by guice.
https://github.com/google/guice/wiki/InjectingProviders
Hi all,
I apologise if my question sounds silly or badly grounded.
I am working on a project which makes intense use of Google Guice and I've
seen several places where the class I am working with uses injected
class WhatEver {
@Inject
WhatEver(Provider<A> providerOfA ...) { ... }
}
I do not understand how/what implements the provider as I do not see any
class around my module explicitly implementing the interface.
Provider<A>
I am pretty sure there is not any.
How does that work ? Are providers synthesised/generated ? If yes I would
like to see where this is done - so I can have a better idea about how the
whole thing works.
Thanks in advance,
Pietro.
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[Stephan Classen]

There are many different implementations depending on the scope and the
binding.
An incomplete list is:
- InjectorImpl.getProviderOrThrow()
- Scopes.SINGLETON
- ProviderLookup.getProvider()
- Providers.of()
- Providers.gucify()

In the end it doesn't matter which implementation is actually injected.
The main things you need to know is what a provider is good for:
- Delayed injection (because something is expensive to create or only
available in a specific scope)
- Multiple injection (because you need more than one instance off it. If
this is the case think twice if you need DI for this class or rather a
factory)
- Provide your own Provider (if you implement a custom scope)

Post by c***@gmail.com
I was reading that page but I can't find where it explicitly says they
are generated. Would you know where the code that generates them is ?
Yes, Providers are generated on the fly by guice.
https://github.com/google/guice/wiki/InjectingProviders
<https://github.com/google/guice/wiki/InjectingProviders>

Post by c***@gmail.com
Hi all,
I apologise if my question sounds silly or badly grounded.
I am working on a project which makes intense use of Google Guice
and I've seen several places where the class I am working with
|
classWhatEver{
@Inject
WhatEver(Provider<A>providerOfA ...){...}
}
|
I do not understand how/what implements the provider as I do not
see any class around my module explicitly implementing the interface.
|
Provider<A>
|
I am pretty sure there is not any.
How does that work ? Are providers synthesised/generated ? If yes
I would like to see where this is done - so I can have a better
idea about how the whole thing works.
Thanks in advance,
Pietro.
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[c***@gmail.com]

Ah ok, thanks.

Post by Stephan Classen
There are many different implementations depending on the scope and the
binding.
- InjectorImpl.getProviderOrThrow()
- Scopes.SINGLETON
- ProviderLookup.getProvider()
- Providers.of()
- Providers.gucify()
In the end it doesn't matter which implementation is actually injected.

That is actually my main interest, I am digging into the
InjectorImpl.getProviderOrThrow() to see where I get. If you have other
userful links such as the ones you just gave me, feel free!

Post by Stephan Classen
- Delayed injection (because something is expensive to create or only
available in a specific scope)
- Multiple injection (because you need more than one instance off it. If
this is the case think twice if you need DI for this class or rather a
factory)
- Provide your own Provider (if you implement a custom scope)
I was reading that page but I can't find where it explicitly says they are
generated. Would you know where the code that generates them is ?

Post by Stephan Classen
Yes, Providers are generated on the fly by guice.
https://github.com/google/guice/wiki/InjectingProviders
Hi all,
I apologise if my question sounds silly or badly grounded.
I am working on a project which makes intense use of Google Guice and
I've seen several places where the class I am working with uses injected
class WhatEver {
@Inject
WhatEver(Provider<A> providerOfA ...) { ... }
}
I do not understand how/what implements the provider as I do not see any
class around my module explicitly implementing the interface.
Provider<A>
I am pretty sure there is not any.
How does that work ? Are providers synthesised/generated ? If yes I would
like to see where this is done - so I can have a better idea about how the
whole thing works.
Thanks in advance,
Pietro.
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